Sacrificial anode

ABSTRACT

The opposite ends of the pipe core of a sacrificial anode are bent 90* through an arc having a relatively short radius, of the order of about four times the diameter of the pipe core.

United States Patent 11 1 Wilson et a1. 1 1 Mar. 11, 1975 15 1SACRIFICIAL ANODE 3,021,934 2/1961 Battis et al 204/197 ,0 ,9 6 1962Amble [751 lnvemorsl g g f? 3,616.422 10/1971 Dorem usw; 204/197 r., 0t0 on rt ur, ex. [731 Assignee: Standard Brass and Manufacturing FOREIGNPATENTS OR APPLICATIONS Company, P rt Arthur. 852,154 10/1900 GreatBritain 204/197 Filed Oct 1 1973 719,427 12/1954 Great Britain 1.204/197 [21] App]. No.: 402,360

Primary E.\'an1iner-T. Tung Related Application Data Attorney, Agent, orFirm-Paul & Paul [63] Continuation of Ser. No. 214,207, Dec. 30, 1971,

abandoned.

52 us. (:1 204/197, 204/286, 204/297 R [571 1 ABSTRACT [51] Int. Cl.C23f 13/00 1 I 58 Field of Search 204/148, 197,286,297 R, The f, Of theWe Core 9 d 204/297 M anode are bent 90 through an are having arelatively short radius, of the order of about four times the di- [56]References Cited ameter of the pipe core.

UNITED STATES PATENTS Harris et a1. 204/197 2 Claims, 4 Drawing FiguresPRTENTEU 1 1975 3,870,615

PRIOR ART Fig. 4

BACKGROUND OF THE INVENTION In the electrolytic corrosion of metals,some parts of the surface act as anodes whereas other parts act ascathodes. The anode parts corrode. The cathode parts do not corrode.Protection against such type of corrosion may be provided by making thewhole surface of the metal cathode to a separate anode. Sufficientvoltage must, however, be available between the two electrodes.Sacrificial anodes of zinc, magnesium, or aluminum alloy may provide thepotential. These metals are chemically reactive with the sea water whichacts as the electrolyte, and the sacrificial body is gradually dissolvedand destroyed. This type of protection is known as cathodic protection.It has been used to inhibit corrosion in a wide variety of submergedfacilities and equipments, including underground and undersea pipelines, and the submerged structures of drilling platforms, derricks,steel ship hulls, and others. The protection is provided by weldingsacrificial anodes at spaced intervals along the undersea pipe, or atspaced apart locations on the submerged structures of the drillingplatforms, derricks, and steel ship hulls. Such sacrificial anodes haveheretofore consisted of zinc, magnesium, or aluminum alloy supported ona straight pipe core the opposite ends of which are beveled and weldedby mitered joints to the ends of stanchions or support posts disposed atright angles thereto. The terminal ends of the support posts are thenwelded to the undersea pipeline, platformderrick structure, or steelship hull.

In the prior art sacrificial anode structures decribed above, mechanicalfailures have frequently occurred at the mitered joints, making itnecessary to repair or replace the structure before the sacrificialmaterial has been fully consumed. These mechanical failures haveresulted from the physical shock, stresses, and forces of the sea towhich the sacrificial anode structures are subjected. In an effort toavoid or reduce the frequency of such mechanical failures, efforts havebeen made to achieve deep penetration welds, with X-ray examination ofthe welds a part of the inspection procedure.

SUMMARY OF THE INVENTION A primary object of the present invention is toprovide a sacrificial anode structure which is not subject to mechanicalfailure and which will last until the sacrificial material is consumed.

A more specific object is to provide a sacrificial anode structure whichdoes not require a welded mitered joint.

The foregoing objects are achieved by providing a steel pipe core theprojecting opposite ends of which are bent 90 through a relatively shortarc. We have found that the opposite ends of a 4 inch schedule 80 steelpipe may be bent 90 through an arc of short length and small radius byplacing the pipe core in ajig in a heavy press and bending the oppositeends of the pipe simultaneously. The terminal ends of the bent steelpipe core, which carries the sacrificial anode material on its straightcenter portion, are welded in the usual manner to the undersea pipelineor steel ship hull which is to be protected.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of asacrificial anode structure according to the present invention.

FIG. 2 illustrates the sacrificial anode of FIG. 1 welded to a pipeline,or ship hull, or other body to be protected against corrosion.

FIG. 3 is a view, in section, looking along the line 3-3 of FIG. 2.

FIG. 4 is a fragmentary schematic illustration of the mitered joint ofthe prior art.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIGS. 1,2 and 3, a body 10 of sacrificial anode material, which may be zinc,magnesium or aluminum alloy, is supported on a one-piece steel pipe core20. Opposite end portions 21 and 22 of pipe core 20 are bent through anangle of 90 along an arc whose radius is relatively short.

In a typical case, the body 10 of sacrificial anode ma terial may be 96inches long and have a generally square cross-sectional configurationwith the lengths of the sides being of the order of ten inches.Actually, two of the opposite sides of the sacrificial body are usuallynot parallel but are inclined slightly toward each other.

Typical dimensions may be 9.6 inches each for the non-.

parallel inclined sides, 9.] inches for the shortdimension side, and10.6 inches for the long-dimension side. The anode structure may weighof the order of 725 pounds. The steel pipe core 20 may be 4-inchschedule steel pipe having an outside diameter of 4.5 inches an insidediameter of 3.826 inches, and a wall thickness of 0.337 inches. Pipe 20may have a total length of the order of 154 inches, and the oppositeends 21 and 22 may each have a straight length of about 29 inches beyondthe 96-inch anode body 10. These 29- inch ends 21 and 22 are bent on aradius of 16.0 inches, as measured to the center axis of the pipe core20, with the terminal end of the bent pipe extending tangentially forthree-fourth inch. When so bent, the over-all length of the structure is132.5 inches. Bending of the 4-inch steel pipe is accomplished byplacing the pipe in a jig and employing a powerful press tosimultaneously bend the opposite ends of the pipe.

It will be understood that the foregoing dimensions and values are onlyillustrative and that cores for an odes may be formed out of steel pipein sizes other than 4 inches and that the radii may be other than fourtimes the pipe size. Also, the anodes could weigh more or less than 725pounds.

As illustrated in FIG. 2, the terminal ends of the pipe core 20 of thesacrificial anode structure are welded as at 31 and 32 to the underseapipe line, or the submerged structure of the derrick, or steel shiphull, indicated in FIG. 2 by the reference numeral 40.

The sacrificial anode structure shown in FIG. 3 represents an importantimprovement over that heretofore available. It is very much stronger andmuch less susceptible to fracture and damage by the sea forces to whichit is subjected. A fragmentary illustration of the prior art sacrificialanode is given in FIG. 4 of the drawing. It will be seen from FIG. 4that the pipe core 120, which carries the body of zinc, magnesium, oraluminum alloy 110, is straight and is connected by a welded miteredjoint 121 to pipe support 220, which is welded at 330 to the pipeline tobe protected. The prior art sacrificial anode structure illustrated inFIG. 4 is prone to fracture and failure at the mitered joint 121 and, inmany cases, replacement of the sacrificial anode structure is necessarybefore the anode material 110 has been consumed. This is, of course, avery unsatisfactory situation. It makes it impossible to estimate inadvance as to the expected life of the sacrificial anode, and makesfrequent inspection necessary. This, of course, adds to the cost.

In contrast to the prior art structure illustrated schematically in FIG.4, the new structure illustrated in FIGS. 1, 2 and 3 will now have to bereplaced until the sacrificial anode material has been entirelyconsumed. The time when this should occur can be estimated in advance.Costly inspections prior to that time are avoided. When the sacrificialmaterial is consumed, the protective structure is removed from thestructure 40 being protected and a new sacrificial anode structure iswelded thereto.

What is claimed is:

l. A sacrificial anode structure comprising:

a. a one-piece pipe core of 4-inch Schedule steel pipe having anelongated straight central section and arcuate sections at each oppositeend of said straight section, the radius of curvature of said arcuatesections being about four times the diamebent structure has an overalllength of 132.5 inches.

1. A sacrificial anode structure comprising: a. a one-piece pipe core of4-inch Schedule 80 steel pipe having an elongated straight centralsection and 90* arcuate sections at each opposite end of said straightsection, the radius of curvature of said arcuate sections being aboutfour times the diameter of the pipe core; b. and a body of sacrificialanode material surrounding and supported by the elongated straightcentral section of said pipe, said central section of said pipe emergingfrom opposite ends of the body of anode material.
 1. A sacrificial anodestructure comprising: a. a one-piece pipe core of 4-inch Schedule 80steel pipe having an elongated straight central section and 90* arcuatesections at each opposite end of said straight section, the radius ofcurvature of said arcuate sections being about four times the diameterof the pipe core; b. and a body of sacrificial anode materialsurrounding and supported by the elongated straight central section ofsaid pipe, said central section of said pipe emerging from opposite endsof the body of anode material.